Fix: Prevent UI tearing and improve display of long content

This commit introduces several changes to better manage terminal height and prevent UI tearing, especially when displaying long tool outputs or when the pending history item exceeds the available terminal height.

- Calculate and utilize available terminal height in `App.tsx`, `HistoryItemDisplay.tsx`, `ToolGroupMessage.tsx`, and `ToolMessage.tsx`.
- Refresh the static display area in `App.tsx` when a pending history item is too large, working around an Ink bug (see https://github.com/vadimdemedes/ink/pull/717).
- Truncate long tool output in `ToolMessage.tsx` and indicate the number of hidden lines.
- Refactor `App.tsx` to correctly measure and account for footer height.

Fixes https://b.corp.google.com/issues/414196943

4 files changed, 229 insertions, 140 deletions

diff --git a/packages/cli/src/ui/App.tsx b/packages/cli/src/ui/App.tsx
index 21d6a730..b6275491 100644
--- a/packages/cli/src/ui/App.tsx
+++ b/packages/cli/src/ui/App.tsx
@@ -4,8 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-import { useCallback, useEffect, useMemo, useState } from 'react';
-import { Box, Static, Text, useStdout } from 'ink';
+import { useCallback, useEffect, useMemo, useState, useRef } from 'react';
+import { Box, DOMElement, measureElement, Static, Text, useStdout } from 'ink';
 import { StreamingState, type HistoryItem } from './types.js';
 import { useGeminiStream } from './hooks/useGeminiStream.js';
 import { useLoadingIndicator } from './hooks/useLoadingIndicator.js';
@@ -46,6 +46,7 @@ export const App = ({
   startupWarnings = [],
 }: AppProps) => {
   const { history, addItem, clearItems } = useHistory();
+  const [staticNeedsRefresh, setStaticNeedsRefresh] = useState(false);
   const [staticKey, setStaticKey] = useState(0);
   const refreshStatic = useCallback(() => {
     setStaticKey((prev) => prev + 1);
@@ -55,7 +56,8 @@ export const App = ({
   const [debugMessage, setDebugMessage] = useState<string>('');
   const [showHelp, setShowHelp] = useState<boolean>(false);
   const [themeError, setThemeError] = useState<string | null>(null);
-
+  const [availableTerminalHeight, setAvailableTerminalHeight] =
+    useState<number>(0);
   const {
     isThemeDialogOpen,
     openThemeDialog,
@@ -193,12 +195,51 @@ export const App = ({
 
   // --- Render Logic ---
 
-  // Get terminal width
+  // Get terminal dimensions
+
   const { stdout } = useStdout();
   const terminalWidth = stdout?.columns ?? 80;
+  const terminalHeight = stdout?.rows ?? 24;
+  const footerRef = useRef<DOMElement>(null);
+  const pendingHistoryItemRef = useRef<DOMElement>(null);
+
   // Calculate width for suggestions, leave some padding
   const suggestionsWidth = Math.max(60, Math.floor(terminalWidth * 0.8));
 
+  useEffect(() => {
+    const staticExtraHeight = /* margins and padding */ 3;
+    const fullFooterMeasurement = measureElement(footerRef.current!);
+    const fullFooterHeight = fullFooterMeasurement.height;
+
+    setAvailableTerminalHeight(
+      terminalHeight - fullFooterHeight - staticExtraHeight,
+    );
+  }, [terminalHeight]);
+
+  useEffect(() => {
+    if (!pendingHistoryItem) {
+      return;
+    }
+
+    const pendingItemDimensions = measureElement(
+      pendingHistoryItemRef.current!,
+    );
+
+    // If our pending history item happens to exceed the terminal height we will most likely need to refresh
+    // our static collection to ensure no duplication or tearing. This is currently working around a core bug
+    // in Ink which we have a PR out to fix: https://github.com/vadimdemedes/ink/pull/717
+    if (pendingItemDimensions.height > availableTerminalHeight) {
+      setStaticNeedsRefresh(true);
+    }
+  }, [pendingHistoryItem, availableTerminalHeight, streamingState]);
+
+  useEffect(() => {
+    if (streamingState === StreamingState.Idle && staticNeedsRefresh) {
+      setStaticNeedsRefresh(false);
+      refreshStatic();
+    }
+  }, [streamingState, refreshStatic, staticNeedsRefresh]);
+
   return (
     <Box flexDirection="column" marginBottom={1} width="90%">
       {/*
@@ -219,146 +260,151 @@ export const App = ({
             <Header />
             <Tips />
           </Box>,
-          ...history.map((h) => <HistoryItemDisplay key={h.id} item={h} />),
+          ...history.map((h) => <HistoryItemDisplay availableTerminalHeight={availableTerminalHeight} key={h.id} item={h} />),
         ]}
       >
         {(item) => item}
       </Static>
       {pendingHistoryItem && (
-        <HistoryItemDisplay
-          // TODO(taehykim): It seems like references to ids aren't necessary in
-          // HistoryItemDisplay. Refactor later. Use a fake id for now.
-          item={{ ...pendingHistoryItem, id: 0 }}
-        />
+        <Box ref={pendingHistoryItemRef}>
+          <HistoryItemDisplay
+            availableTerminalHeight={availableTerminalHeight}
+            // TODO(taehykim): It seems like references to ids aren't necessary in
+            // HistoryItemDisplay. Refactor later. Use a fake id for now.
+            item={{ ...pendingHistoryItem, id: 0 }}
+          />
+        </Box>
       )}
       {showHelp && <Help commands={slashCommands} />}
 
-      {startupWarnings.length > 0 && (
-        <Box
-          borderStyle="round"
-          borderColor={Colors.AccentYellow}
-          paddingX={1}
-          marginY={1}
-          flexDirection="column"
-        >
-          {startupWarnings.map((warning, index) => (
-            <Text key={index} color={Colors.AccentYellow}>
-              {warning}
-            </Text>
-          ))}
-        </Box>
-      )}
+      <Box flexDirection="column" ref={footerRef}>
+        {startupWarnings.length > 0 && (
+          <Box
+            borderStyle="round"
+            borderColor={Colors.AccentYellow}
+            paddingX={1}
+            marginY={1}
+            flexDirection="column"
+          >
+            {startupWarnings.map((warning, index) => (
+              <Text key={index} color={Colors.AccentYellow}>
+                {warning}
+              </Text>
+            ))}
+          </Box>
+        )}
 
-      {isThemeDialogOpen ? (
-        <Box flexDirection="column">
-          {themeError && (
-            <Box marginBottom={1}>
-              <Text color={Colors.AccentRed}>{themeError}</Text>
-            </Box>
-          )}
-          <ThemeDialog
-            onSelect={handleThemeSelect}
-            onHighlight={handleThemeHighlight}
-            settings={settings}
-            setQuery={setQuery}
-          />
-        </Box>
-      ) : (
-        <>
-          <LoadingIndicator
-            isLoading={streamingState === StreamingState.Responding}
-            currentLoadingPhrase={currentLoadingPhrase}
-            elapsedTime={elapsedTime}
-          />
-          {isInputActive && (
-            <>
-              <Box
-                marginTop={1}
-                display="flex"
-                justifyContent="space-between"
-                width="100%"
-              >
-                <Box>
-                  <Text color={Colors.SubtleComment}>cwd: </Text>
-                  <Text color={Colors.LightBlue}>
-                    {shortenPath(config.getTargetDir(), 70)}
-                  </Text>
-                </Box>
+        {isThemeDialogOpen ? (
+          <Box flexDirection="column">
+            {themeError && (
+              <Box marginBottom={1}>
+                <Text color={Colors.AccentRed}>{themeError}</Text>
               </Box>
-
-              <InputPrompt
-                query={query}
-                onChange={setQuery}
-                onChangeAndMoveCursor={onChangeAndMoveCursor}
-                editorState={editorState}
-                onSubmit={handleFinalSubmit} // Pass handleFinalSubmit directly
-                showSuggestions={completion.showSuggestions}
-                suggestions={completion.suggestions}
-                activeSuggestionIndex={completion.activeSuggestionIndex}
-                userMessages={userMessages} // Pass userMessages
-                navigateSuggestionUp={completion.navigateUp}
-                navigateSuggestionDown={completion.navigateDown}
-                resetCompletion={completion.resetCompletionState}
-                setEditorState={setEditorState}
-                onClearScreen={handleClearScreen} // Added onClearScreen prop
-              />
-              {completion.showSuggestions && (
-                <Box>
-                  <SuggestionsDisplay
-                    suggestions={completion.suggestions}
-                    activeIndex={completion.activeSuggestionIndex}
-                    isLoading={completion.isLoadingSuggestions}
-                    width={suggestionsWidth}
-                    scrollOffset={completion.visibleStartIndex}
-                    userInput={query}
-                  />
+            )}
+            <ThemeDialog
+              onSelect={handleThemeSelect}
+              onHighlight={handleThemeHighlight}
+              settings={settings}
+              setQuery={setQuery}
+            />
+          </Box>
+        ) : (
+          <>
+            <LoadingIndicator
+              isLoading={streamingState === StreamingState.Responding}
+              currentLoadingPhrase={currentLoadingPhrase}
+              elapsedTime={elapsedTime}
+            />
+            {isInputActive && (
+              <>
+                <Box
+                  marginTop={1}
+                  display="flex"
+                  justifyContent="space-between"
+                  width="100%"
+                >
+                  <Box>
+                    <Text color={Colors.SubtleComment}>cwd: </Text>
+                    <Text color={Colors.LightBlue}>
+                      {shortenPath(config.getTargetDir(), 70)}
+                    </Text>
+                  </Box>
                 </Box>
-              )}
-            </>
-          )}
-        </>
-      )}
 
-      {initError && streamingState !== StreamingState.Responding && (
-        <Box
-          borderStyle="round"
-          borderColor={Colors.AccentRed}
-          paddingX={1}
-          marginBottom={1}
-        >
-          {history.find(
-            (item) => item.type === 'error' && item.text?.includes(initError),
-          )?.text ? (
-            <Text color={Colors.AccentRed}>
-              {
-                history.find(
-                  (item) =>
-                    item.type === 'error' && item.text?.includes(initError),
-                )?.text
-              }
-            </Text>
-          ) : (
-            <>
-              <Text color={Colors.AccentRed}>
-                Initialization Error: {initError}
-              </Text>
+                <InputPrompt
+                  query={query}
+                  onChange={setQuery}
+                  onChangeAndMoveCursor={onChangeAndMoveCursor}
+                  editorState={editorState}
+                  onSubmit={handleFinalSubmit} // Pass handleFinalSubmit directly
+                  showSuggestions={completion.showSuggestions}
+                  suggestions={completion.suggestions}
+                  activeSuggestionIndex={completion.activeSuggestionIndex}
+                  userMessages={userMessages} // Pass userMessages
+                  navigateSuggestionUp={completion.navigateUp}
+                  navigateSuggestionDown={completion.navigateDown}
+                  resetCompletion={completion.resetCompletionState}
+                  setEditorState={setEditorState}
+                  onClearScreen={handleClearScreen} // Added onClearScreen prop
+                />
+                {completion.showSuggestions && (
+                  <Box>
+                    <SuggestionsDisplay
+                      suggestions={completion.suggestions}
+                      activeIndex={completion.activeSuggestionIndex}
+                      isLoading={completion.isLoadingSuggestions}
+                      width={suggestionsWidth}
+                      scrollOffset={completion.visibleStartIndex}
+                      userInput={query}
+                    />
+                  </Box>
+                )}
+              </>
+            )}
+          </>
+        )}
+
+        {initError && streamingState !== StreamingState.Responding && (
+          <Box
+            borderStyle="round"
+            borderColor={Colors.AccentRed}
+            paddingX={1}
+            marginBottom={1}
+          >
+            {history.find(
+              (item) => item.type === 'error' && item.text?.includes(initError),
+            )?.text ? (
               <Text color={Colors.AccentRed}>
-                {' '}
-                Please check API key and configuration.
+                {
+                  history.find(
+                    (item) =>
+                      item.type === 'error' && item.text?.includes(initError),
+                  )?.text
+                }
               </Text>
-            </>
-          )}
-        </Box>
-      )}
+            ) : (
+              <>
+                <Text color={Colors.AccentRed}>
+                  Initialization Error: {initError}
+                </Text>
+                <Text color={Colors.AccentRed}>
+                  {' '}
+                  Please check API key and configuration.
+                </Text>
+              </>
+            )}
+          </Box>
+        )}
 
-      <Footer
-        config={config}
-        debugMode={config.getDebugMode()}
-        debugMessage={debugMessage}
-        cliVersion={cliVersion}
-        geminiMdFileCount={geminiMdFileCount}
-      />
-      <ConsoleOutput />
+        <Footer
+          config={config}
+          debugMode={config.getDebugMode()}
+          debugMessage={debugMessage}
+          cliVersion={cliVersion}
+          geminiMdFileCount={geminiMdFileCount}
+        />
+        <ConsoleOutput />
+      </Box>
     </Box>
   );
 };
diff --git a/packages/cli/src/ui/components/HistoryItemDisplay.tsx b/packages/cli/src/ui/components/HistoryItemDisplay.tsx
index 0c724feb..bd35d335 100644
--- a/packages/cli/src/ui/components/HistoryItemDisplay.tsx
+++ b/packages/cli/src/ui/components/HistoryItemDisplay.tsx
@@ -16,10 +16,12 @@ import { Box } from 'ink';
 
 interface HistoryItemDisplayProps {
   item: HistoryItem;
+  availableTerminalHeight: number;
 }
 
 export const HistoryItemDisplay: React.FC<HistoryItemDisplayProps> = ({
   item,
+  availableTerminalHeight,
 }) => (
   <Box flexDirection="column" key={item.id}>
     {/* Render standard message types */}
@@ -31,7 +33,11 @@ export const HistoryItemDisplay: React.FC<HistoryItemDisplayProps> = ({
     {item.type === 'info' && <InfoMessage text={item.text} />}
     {item.type === 'error' && <ErrorMessage text={item.text} />}
     {item.type === 'tool_group' && (
-      <ToolGroupMessage toolCalls={item.tools} groupId={item.id} />
+      <ToolGroupMessage
+        toolCalls={item.tools}
+        groupId={item.id}
+        availableTerminalHeight={availableTerminalHeight}
+      />
     )}
   </Box>
 );
diff --git a/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx b/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx
index 35408114..33460405 100644
--- a/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx
+++ b/packages/cli/src/ui/components/messages/ToolGroupMessage.tsx
@@ -14,18 +14,23 @@ import { Colors } from '../../colors.js';
 interface ToolGroupMessageProps {
   groupId: number;
   toolCalls: IndividualToolCallDisplay[];
+  availableTerminalHeight: number;
 }
 
 // Main component renders the border and maps the tools using ToolMessage
 export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
   groupId,
   toolCalls,
+  availableTerminalHeight,
 }) => {
   const hasPending = !toolCalls.every(
     (t) => t.status === ToolCallStatus.Success,
   );
   const borderColor = hasPending ? Colors.AccentYellow : Colors.SubtleComment;
 
+  const staticHeight = /* border */ 2 + /* marginBottom */ 1;
+  availableTerminalHeight -= staticHeight;
+
   return (
     <Box
       key={groupId}
@@ -46,13 +51,14 @@ export const ToolGroupMessage: React.FC<ToolGroupMessageProps> = ({
       {toolCalls.map((tool) => (
         <Box key={groupId + '-' + tool.callId} flexDirection="column">
           <ToolMessage
-            key={tool.callId} // Use callId as the key
-            callId={tool.callId} // Pass callId
+            key={tool.callId}
+            callId={tool.callId}
             name={tool.name}
             description={tool.description}
             resultDisplay={tool.resultDisplay}
             status={tool.status}
-            confirmationDetails={tool.confirmationDetails} // Pass confirmationDetails
+            confirmationDetails={tool.confirmationDetails}
+            availableTerminalHeight={availableTerminalHeight}
           />
           {tool.status === ToolCallStatus.Confirming &&
             tool.confirmationDetails && (
diff --git a/packages/cli/src/ui/components/messages/ToolMessage.tsx b/packages/cli/src/ui/components/messages/ToolMessage.tsx
index 3b58c052..220578de 100644
--- a/packages/cli/src/ui/components/messages/ToolMessage.tsx
+++ b/packages/cli/src/ui/components/messages/ToolMessage.tsx
@@ -12,14 +12,38 @@ import { DiffRenderer } from './DiffRenderer.js';
 import { Colors } from '../../colors.js';
 import { MarkdownDisplay } from '../../utils/MarkdownDisplay.js';
 
-export const ToolMessage: React.FC<IndividualToolCallDisplay> = ({
+export interface ToolMessageProps extends IndividualToolCallDisplay {
+  availableTerminalHeight: number;
+}
+
+export const ToolMessage: React.FC<ToolMessageProps> = ({
   name,
   description,
   resultDisplay,
   status,
+  availableTerminalHeight,
 }) => {
   const statusIndicatorWidth = 3;
   const hasResult = resultDisplay && resultDisplay.toString().trim().length > 0;
+  const staticHeight = /* Header */ 1;
+  availableTerminalHeight -= staticHeight;
+
+  let displayableResult = resultDisplay;
+  let hiddenLines = 0;
+
+  // Truncate the overall string content if it's too long.
+  // MarkdownRenderer will handle specific truncation for code blocks within this content.
+  if (typeof resultDisplay === 'string' && resultDisplay.length > 0) {
+    const lines = resultDisplay.split('\n');
+    // Estimate available height for this specific tool message content area
+    // This is a rough estimate; ideally, we'd have a more precise measurement.
+    const contentHeightEstimate = availableTerminalHeight - 5; // Subtracting lines for tool name, status, padding etc.
+    if (lines.length > contentHeightEstimate && contentHeightEstimate > 0) {
+      displayableResult = lines.slice(0, contentHeightEstimate).join('\n');
+      hiddenLines = lines.length - contentHeightEstimate;
+    }
+  }
+
   return (
     <Box paddingX={1} paddingY={0} flexDirection="column">
       <Box minHeight={1}>
@@ -56,15 +80,22 @@ export const ToolMessage: React.FC<IndividualToolCallDisplay> = ({
       </Box>
       {hasResult && (
         <Box paddingLeft={statusIndicatorWidth} width="100%">
-          <Box flexDirection="row">
-            {/* Use default text color (white) or gray instead of dimColor */}
-            {typeof resultDisplay === 'string' && (
+          <Box flexDirection="column">
+            {typeof displayableResult === 'string' && (
               <Box flexDirection="column">
-                <MarkdownDisplay text={resultDisplay} />
+                <MarkdownDisplay text={displayableResult} />
               </Box>
             )}
-            {typeof resultDisplay === 'object' && (
-              <DiffRenderer diffContent={resultDisplay.fileDiff} />
+            {typeof displayableResult === 'object' && (
+              <DiffRenderer diffContent={displayableResult.fileDiff} />
+            )}
+            {hiddenLines > 0 && (
+              <Box>
+                <Text color={Colors.SubtleComment}>
+                  ... {hiddenLines} more line{hiddenLines === 1 ? '' : 's'}{' '}
+                  hidden ...
+                </Text>
+              </Box>
             )}
           </Box>
         </Box>